Question

Write a C++ program to run a menu-driven program with the following choices:

1. Count number of even digits in a number
2. Compute the factorial of a number
3. Quit

Make sure your program conforms to the following requirements:
1. This program should be called playingWithNumbers.cpp

2. Write a function called getValidUserInputPosNumGT0 that allows a user to enter an integer and validated that the number is > 0. It must have a pass by reference parameter that will store the value selected by the user.

3. Write a function called numEvenDigits that takes a number as a value parameter and returns the count of how many digits in the number are even.

4. Write a function called factorial that takes a number as a value parameter and returns the factorial of the number.

n! = n * (n-1) * (n-2) * ...1

5. Add comments wherever necessary.

Sample Runs:

NOTE: not all possible runs are shown below.

Sample Run

Welcome to the playing with numbers!
1) Count the even digits in a number
2) Compute the factorial of a number
3) Quit
Select an option (1..4)..9
Select an option (1..4)..-9
Select an option (1..4)..1
Enter in a positive number greater than 0...12
numEvenDigits(12)= 1
1) Count the even digits in a number
2) Compute the factorial of a number
3) Quit
Select an option (1..4)..1
Enter in a positive number greater than 0...22
numEvenDigits(22)= 2
1) Count the even digits in a number
2) Compute the factorial of a number
3) Quit
Select an option (1..4)..1
Enter in a positive number greater than 0...1345
numEvenDigits(1345)= 1
1) Count the even digits in a number
2) Compute the factorial of a number
3) Quit
Select an option (1..4)..1
Enter in a positive number greater than 0...2461
numEvenDigits(2461)= 3
1) Count the even digits in a number
2) Compute the factorial of a number
3) Quit
Select an option (1..4)..2
Enter in a positive number greater than 0...1
Factorial(1) = 1
1) Count the even digits in a number
2) Compute the factorial of a number
3) Quit
Select an option (1..4)..2
Enter in a positive number greater than 0...2
Factorial(2) = 2
1) Count the even digits in a number
2) Compute the factorial of a number
3) Quit
Select an option (1..4)..2
Enter in a positive number greater than 0...3
Factorial(3) = 6
1) Count the even digits in a number
2) Compute the factorial of a number
3) Quit
Select an option (1..4)..2
Enter in a positive number greater than 0...4
Factorial(4) = 24
1) Count the even digits in a number
2) Compute the factorial of a number
3) Quit
Select an option (1..4)..2
Enter in a positive number greater than 0...5
Factorial(5) = 120
1) Count the even digits in a number
2) Compute the factorial of a number
3) Quit
Select an option (1..4)..3

Process finished with exit code 0

Answer 1

ANSWER:-

#include <iostream>

using namespace std;

void getValidUserInputPosNumGT0(int *a){
    int num;
    // prompt user to enter number
    cout<<"Enter in a positive number greater than 0...";
    // store it by reference
    cin>>*a;
}
int numEvenDigits(int num){
    int noOfEvenDigits = 0;
    while(num > 0){
        // It gives remainder, i.e last of the number
        // if it is even then increase noOfEvenDigits by 1
        int digit = num%10;
        if(digit%2==0){
            noOfEvenDigits++;
        }
        num = num/10;
    }
    return noOfEvenDigits;
}
int factorial(int num){
    int fact = 1;
    while(num>1){
        fact *= num;
        num--;
    }
    return fact;
}
int main()
{   int ch,num;
    cout<<"Welcome to the playing with numbers!"<<endl;
    do{
        cout<<"1) Count the even digits in a number"<<endl;
        cout<<"2) Compute the factorial of a number"<<endl;
        cout<<"3) Quit"<<endl;
        while(true){
            cout<<"Select an option(1..4)..";
            cin>>ch;
            if(ch==1 || ch==2 || ch==3){
                break;
            }
        }
        switch(ch){
            case 1:
                getValidUserInputPosNumGT0(&num);
                cout<<"numEvenDigits("<<num<<")="<<numEvenDigits(num)<<endl;
                break;
            case 2:
                getValidUserInputPosNumGT0(&num);
                cout<<"Factorial("<<num<<")="<<factorial(num)<<endl;
                break;
        }
    }while(ch!=3);
    return 0;
}

OUTPUT:-

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